scholarly journals Hybrid and intermittent drying of carrot (Daucus carota var. Nantes)

2018 ◽  
Author(s):  
Dominik Mierzwa ◽  
Justyna Szadzińska ◽  
Krzysztof Bukowski
Keyword(s):  
Mass Transfer ◽  
Convective Drying ◽  
Drying Rate ◽  
Hot Air Drying ◽  
Drying Time ◽  
Air Drying ◽  
Hot Air ◽  
Intermittent Mode ◽  
Airborne Ultrasound

A combination of high power airborne ultrasound and microwaves in hot air drying was developed to investigate the effect of intermittent mode on process effectiveness and quality of carrot. The drying experiments were carried out in an innovative hybrid dryer. The course of moisture ratio, drying rate, specific energy and water consumption, colour, water activity and shrinkage were discussed. The results showed that intermittent ultrasound and microwaves in convective drying accelerate the heat and mass transfer, leading to shorter drying time and faster drying rate. It was found that hybrid-intermittent drying can improve the energy efficiency and product quality. Keywords: intermittent drying; ultrasound; microwaves; energy; shrinkage

Effects of drying methods on color retention and chlorophyll of celery (ApiumgraveolensL.), spinach (Spinacia oleraceaL.), Malabar spinach (Basella albaL.)

2020 ◽  
pp. 53-61
Author(s):  
Dat Q Tran
Keyword(s):  
Microwave Drying ◽  
Drying Methods ◽  
Hot Air Drying ◽  
Drying Time ◽  
Air Drying ◽  
Color Retention ◽  
Hot Air ◽  
Drying Techniques ◽  
Dried Vegetables

Dried vegetables are considered convenient for storage, transportation and preservation. The different drying techniques could influence the quality of resulting products. This study aimed to evaluate the effects of three distinguish drying methods as hot-air drying, foam-mat drying and microwave drying on the color retention and chlorophyll of green vegetables powder. Fresh spinach(Spinacia oleraceaL.), celery (Apium graveolensL.), Malabar spinach (Basella albaL.) were dried by different methods: hot air at 60oC, foam-mat at 60oC and microwave at 270 W until the samples reached approximately 9% of moisture content (wb). The drying time of the dried samples by microwave, foam-mat and hot-air method were 60, 210 and 240 min, respectively. Foam-mat dried vegetables were found to have the best quality in terms of color and the residual chlorophyll content. The findings suggest that foam-mat drying is promising in dried vegetable processing

Kinetics of Microwave Vacuum Drying of “Cat Chu” Mango in Mekong Delta - Vietnam

2015 ◽  
Vol 656-657 ◽  
pp. 573-579 ◽  
Author(s):  
Cuong Nguyen Van ◽  
Hau Tran Tan
Keyword(s):  
Mekong Delta ◽  
Convective Drying ◽  
Vacuum Drying ◽  
Second Phase ◽  
High Quality ◽  
Hot Air Drying ◽  
Drying Time ◽  
Air Drying ◽  
Microwave Vacuum Drying ◽  
Hot Air

Microwave vacuum drying is one of innovative drying techniques that is today used in drying of foods, medical products and other high quality products. In this drying technology, heat is generated by directly transforming the electromagnetic energy into kinetic molecular energy of water, thus the heat is produced deep within the material to be dried under vacuum environment. This paper presents the results of research on microwave vacuum drying of “Cat Chu” mango in Mekong Delta – Vietnam. “Cat Chu” mango, with moisture content of (80 ± 1) % (wet basis - wb), was sliced into 5 cm thickness, and was dried in mWaveVac0150-lc dryer (Püschner - Germany). The drying vacuum was from 60 to 120 mbar. Three levels of microwave power were established: the first phase from 600 to 800 W, the second phase from 300 to 500 W, the last one from 150 to 250 W. The control sample was dried by convective drying method at 60 °C; and vacuum drying at 70 mbar, 60 °C. The results of this research showed that high quality product in terms of color, surface shrinkage and structure was obtained by microwave vacuum drying. The drying time was about 45 min, 450 min and 870 min with microwave vacuum drying, vacuum drying and convective hot-air drying, respectively. In addition, Fick’s equation and Crank’s solution were applied to analyze and calculate the accessibility and diffusion coefficient of microwave vacuum drying process. Starting accessibility of process was significantly increased; the diffusivity obtained was within a range from 6.44*10-10 m2/s to 16.16*10-10 m2/s. The results also indicated that there was a higher exchange in surface and a greater internal diffusion of experimental microwave vacuum drying samples compared to the control vacuum and hot-air drying samples.

Hot-air Drying Kinetics of Yam Slices under Step Change in Relative Humidity

2016 ◽  
Vol 12 (8) ◽  
pp. 783-792 ◽  
Author(s):  
Hao-Yu Ju ◽  
Qian Zhang ◽  
A.S. Mujumdar ◽  
Xiao-Ming Fang ◽  
Hong-Wei Xiao ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Weibull Model ◽  
Moisture Diffusivity ◽  
Drying Kinetics ◽  
Drying Rate ◽  
Rehydration Ratio ◽  
Hot Air Drying ◽  
Drying Time ◽  
Air Drying ◽  
Hot Air

Abstract The drying kinetics and mathematical modeling of hot-air drying of yam slices were investigated under two-stage relative humidity (RH) control strategy with 60 °C and 1.5 m/s as its constant drying temperature and air velocity, respectively. Results indicate high RH in the initial stage results in high sample’s temperature that enhances water diffusion in the falling rate drying period. Within the scope of current work, change in RH in the later drying period has insignificant influence on sample’s temperature rise while low RH can accelerate the drying rate. Compared to drying at constant 20 % RH at the same drying air temperature, the drying strategy of using 40 % RH over the first 15 min and then lowing to 20 % RH for the remainder time yields a shorter drying time. Weibull model adequately described the moisture content variation with time for all experiments with the scale parameter ranging from 105.02 to 122.38 min and the values of shape parameters from 0.988 to 1.183. The effective moisture diffusivity determined from the Weibull model varied from 2.032 to 2.610×10−8 m2/s. The rehydration ratio increased as the overall drying time was reduced. Microstructure examination shows that higher RH in the initial drying stage can lead to a more porous microstructure which enhances drying, while fast drying rate in the initial drying period generates a crust layer which hinders drying.

Drying Characteristics and Quality of Fresh White Waxy Corn Under Different Drying Methods

2021 ◽  
Author(s):  
Yanling He ◽  
Dan Huang ◽  
Yongjia Chen ◽  
Kaiyang Men ◽  
S. A. Sherif ◽  
...  
Keyword(s):  
Far Infrared ◽  
Drying Rate ◽  
Hot Air Drying ◽  
Drying Time ◽  
Air Drying ◽  
Infrared Drying ◽  
Sun Drying ◽  
Hot Air ◽  
Waxy Corn ◽  
Drying Quality

Abstract The drying characteristics and drying quality of fresh white waxy corn were investigated under three different drying methods (sun drying, hot-air drying and far-infrared drying) and different drying temperatures (55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C). The optimal drying method and drying condition were obtained by comparing the drying time and drying quality including damage rate, rehydration capacity and the contents of protein, fatty acid and starch. The results showed that the drying time of sun drying was the longest, while the drying quality was the best, i.e., the damage rate was the lowest and the nutrient retention was the highest. The far-infrared drying time was shorter and the quality was better than that of hot air drying. The higher the temperature, the faster the drying rate. The optimal drying temperature was 60 °C under far-infrared drying, which can effectively remove the water and keep the food quality. Besides, the drying rate was faster than hot air, and the color of the dried products was brighter. When hot air drying was used, the value of fatty acids did not change much below 65 °C, but it rose sharply above 65 °C. The optimal drying temperature was 65 °C, under which the drying rate was moderate and the quality was relatively good. If the production cost was considered, sun drying was the best, following the 60 °C far-infrared drying. This conclusion can provide a reference for the drying conditions of corn after harvest in agricultural production, and to a certain extent provide suggestions for the later drying treatment methods and treatment temperatures of fresh white waxy corn.

scholarly journals Ultrasound-Enhanced Hot Air Drying of Germinated Highland Barley Seeds: Drying Characteristics, Microstructure, and Bioactive Profile

2019 ◽  
Vol 1 (4) ◽  
pp. 496-510
Author(s):  
Yan Song ◽  
Yang Tao ◽  
Xiaoyu Zhu ◽  
Yongbin Han ◽  
Pau Loke Show ◽  
...  
Keyword(s):  
Phenolic Content ◽  
Original Structure ◽  
Hot Air Drying ◽  
Drying Time ◽  
Air Drying ◽  
Drying Characteristics ◽  
Organic Selenium ◽  
Hot Air ◽  
Highland Barley

The effects of ultrasound-enhanced hot air drying on the drying characteristics, microstructure and bioactive profile of germinated highland barley seeds (GHB) were studied. GHB was dried by hot air at 55 °C and 70 °C and ultrasonic intensities of 125.1 W/dm2 and 180.2 W/dm2, respectively. The results showed that when the drying temperature was 55 °C or 70 °C, the sonicated groups could shorten the drying time by 17.4–26.1% or 18.8–31.3%, respectively. Ultrasound drying at 125.1 W/dm2 and 55 °C could mostly increase the content of organic selenium and the rehydration rate, improve the color and maintain the original structure of GHB. Compared with hot air drying alone, the phenolic content did not increase due to ultrasound-enhanced hot air drying. Therefore, drying at an ultrasonic intensity of 125.1 W/dm2 and a temperature of 55 °C could effectively shorten the drying time, and enhance the quality of GHB.

scholarly journals 3D model simulating the hydro-mechanical state of unsaturated and deformable material during hot air drying

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Lamine Hassini
Keyword(s):  
Fluid Pressure ◽  
Convective Drying ◽  
Von Mises Stress ◽  
Mechanical State ◽  
Three Dimensional Model ◽  
Hot Air Drying ◽  
Drying Time ◽  
Air Drying ◽  
Hot Air ◽  
Deformable Material

A three dimensional model to predict the hydro-mechanical state of unsaturated and deformable material during hot air drying has been proposed. The material viscoelastic behaviour was formulated using Bishop’s effective stress theory for partially saturated material using the liquid saturation as the Bishop parameter. The hydro-thermal and mechanical equations were coupled by the fluid pressure and the solid matter velocity. The model was applied to a deformable material (innovative clay-cellulose fibers composite) subjected to convective drying. A generalized Maxwell model with five elements, whose parameters were measured experimentally and correlated to water content was used to describe the material’s viscoelastic behavior. The hydro-thermal part of the proposed model was validated on the basis of a  comparison of experimental and simulated drying rate curves. The Von Mises stress was simulated and compared to the experimental tensile strength in order to predict the time and the region of material failure.  For a drying process at95°C, the region of failure risk was identified. The failure may occur on the lateral surface of the slab in contact with air at a drying time of 2.5h.

The influence of inhibit avoid water defect responses by heat pretreatment on hot air drying rate of spinach

2016 ◽  
Vol 168 ◽  
pp. 113-118 ◽  
Author(s):  
Takashi Watanabe ◽  
Takahiro Orikasa ◽  
Hiroshi Shono ◽  
Shoji Koide ◽  
Yasumasa Ando ◽  
...  
Keyword(s):  
Drying Rate ◽  
Hot Air Drying ◽  
Air Drying ◽  
Heat Pretreatment ◽  
Hot Air

Determination of Antioxidant Activity of Edible Calendula Flowers by Hot-air Drying Time

2018 ◽  
Vol 26 (4) ◽  
pp. 202-208
Author(s):  
Sang Im Oh ◽  
Seo Young Kim ◽  
Ja Hee Lee ◽  
Ae Kyung Lee
Keyword(s):  
Antioxidant Activity ◽  
Hot Air Drying ◽  
Drying Time ◽  
Air Drying ◽  
Hot Air
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